Upconversion NaYF 4 :Yb/Er-TiO 2 -Ti 3 C 2 Heterostructure-Based Near-Infrared Light-Driven Photoelectrochemical Biosensor for Highly Sensitive and Selective d-Serine Detection.

A near-infrared (NIR) light-driven NaYF 4 :Yb/Er-TiO 2 -Ti 3 C 2 (NYF-TiO 2 -Ti 3 C 2 ) heterostructure-based photoelectrochemical (PEC) biosensing platform was constructed for highly sensitive d-serine (d-ser) detection. Accurate d-ser detection depends on the model biocatalyst, d-amino acid oxidase (DAAO), which converts d-ser into hydroxypyruvate and an equimolar concentration of hydrogen peroxide (H 2 O 2 ) via an enzymatic reaction. The TiO 2 -Ti 3 C 2 semiconductor and NaYF 4 :Yb/Er optical transducer formed a Schottky junction that provided an irreversible channel for electron transfer. Infrared light was converted into absorbable multiemission light, thereby effectively increasing light absorption. Simultaneously, the generated H 2 O 2 rapidly scavenged photogenerated holes to separate electron-hole pairs, which amplified the photocurrent signal. Under optimal conditions, the NIR light-driven PEC biosensor exhibited an excellent PEC performance for d-ser detection, with a wide linear range of 2-1650 μmol L -1 and detection limit as low as 0.286 μmol L -1 . Importantly, high detection reproducibility and accuracy were achieved using this strategy for analyzing human serum and rat cerebrospinal fluid (CSF) specimens. The admirable applicability of the NYF-TiO 2 -Ti 3 C 2 -based PEC biosensor for detecting d-ser may lead to further opportunities for detecting other disease-related biomarkers.